1. Field of the Invention
This invention relates to a rotary head type digital signal playback for regenerating, for example, video and audio signals recorded in a digital form.
2. Background of the Invention
There is known a device for regenerating video and audio signals recorded on a magnetic tape in a digital form using rotary heads. In this case, the rotary heads having different azimuth angles are generally used to record signals on tracks adjacent to each other so that crosstalk caused by interference with one another can be removed at the time of playback even if one track is provided closely adjacent to another for high-density recording purposes.
Normally, two rotary heads having different azimuth angles are fitted to a drum, the two rotary heads being installed 180.degree. apart from each other. The two heads are used to alternately form diagonal magnetic tracks on a magnetic tape for recording signals.
In consequence, the signal will not be regenerated unless the rotary head properly scan the track along the azimuth angle at the time of playback.
Referring to the accompanying drawings, the above fundamental fact will be described. FIG. 1 is a diagram showing magnetic tracks recorded on a magnetic tape 1 with the movements (loci) of the magnetic heads over the traveling tape 1. The magnetic tracks T.sub.a and T.sub.b having different azimuth angles are recorded on the magnetic tape 1 alternately without guard bands. In FIG. 1, a and b designate the two azimuth angles of the recorded track T.sub.a and T.sub.b.
Assume that the magnetic tape 1 is played back using two rotary heads fitted to the rotary drum and having the different azimuth angles and also assume that, as shown in FIG. 1, the two rotary heads scan the magnetic tape in a direction different from that of the tracks T.sub.a and T.sub.b recorded thereon because of the malfunction of the travel mechanism. There results different scanning loci 2 and 3. A and B represent the azimuth angle of each head with A=a and B=b.
In the above situation, each of the two rotary heads is capable of regenerating a signal from only the magnetic track portion conforming to the proper azimuth angle, i.e., the portion having slanted lines. In other words, there is a portion left unread on each magnetic track and, as that portion left unread increases, error correction in the digital signal playback system and consequently complete playback become impossible. In this case, digital audio signals are seriously affected thereby.
For the above reasons, it is absolutely necessary to accurately regulate tape travel, precisely machine the drum and thoroughly adjust the head positions in order to prevent the scanning directions from shifting even in the case of a conventional device for use in playback only.
However, it is quite troublesome regulating tape travel, precisely machining the drum and adjusting the head positions. In addition, such arrangements have caused an increase in cost.